Earliest curry in Southeast Asia and the global spice trade 2000 years ago

The global spice trade has played an essential role in world history. However, because of poor preservation conditions, archaeobotanical remains of spices have been limited in archaeological contexts until now. This study reports evidence for spice processing from the archaeological site of Oc Eo in southern Vietnam, an entrepôt of the state of Funan that was occupied during the early centuries CE. Analysis of plant microremains recovered from the surfaces of Oc Eo grinding stone tools thought to be of South Asian origin has identified culinary spices that include turmeric, ginger, fingerroot, sand ginger, galangal, clove, nutmeg, and cinnamon. These spices are indispensable ingredients used in the making of curry in South Asia today. We suggest that South Asian migrants or visitors introduced this culinary tradition into Southeast Asia during the period of early trade contact via the Indian Ocean, commencing about 2000 years ago.

The archaeological region of Oc Eo covers an area of some 2,500 ha, and includes two adjacent areas, these being the lower slopes and summits of Mount Ba The, and the floodplain to its south that contains several low-lying mounds, including the eponymous site named Go (mound) Oc Eo (69) (fig. S2). On the eastern flank of Mount Ba The, the Linh Son group of religious foundations occupies an area of about 800 by 400 m (fig. S2). In Go Oc Eo, residential areas were distributed along canals, and nearly 70 wooden stakes from former stilt dwellings have been excavated in waterlogged deposits at Lung Lon B ( fig. S3). The artifacts found here were mainly occupation and economic refuse, including potsherds and artifacts of stone, terracotta, wood, metal and glass, with varied food remains (e.g., fish bones, animal bones, tree nuts).
The rich collections of imported artifacts discovered by Malleret show that Oc Eo had strong and diverse external trade relations with the Roman, Byzantine, Islamic, South Asian, and Chinese spheres of influence that spanned the 2nd to 8th centuries CE (84). Striking examples include coins and medallions of Roman inspiration, a gold ring decorated with a symbol of Nandi (the bovine mount of Shiva), an Eastern Han bronze mirror and Wu Zhu coins, and gold beads of possible Mediterranean origin (2nd-3rd centuries CE) (14) (fig. S4).

Details of the starch grain identifications 1. Spices (1) Turmeric (Curcuma longa)
Starch grains from turmeric (Type Ia) account for the largest proportion of the Zingiberaceae. They are elongated and ovate in shape with an eccentric protruding hilum (Fig. 7, A-a, B-b; Fig. 8, A-a). Turmeric starch grains are the largest in size among our starch findings, ranging in length from 12.69μm to 45.54μm, with a mean of 25.4±6.37μm. Given that turmeric usually is consumed as powder, we investigated the morphology of modern turmeric powder for comparison. We noted that the ancient grains, like the modern turmeric powder, commonly showed flat surfaces, loss of lamellae, and highly weakened extinction crosses. These were due to damage caused by grinding activities (Fig. 8, B-b).
(2) Ginger (Zingiber officinale) Eighty-three small oval starch grains (Type Ib) with protruding hila are identified (Fig. 7, C-c; Fig. 8, C-c) as from ginger. Their most noticeable feature is that the widths of about one-third of the sample are larger than their lengths, with 90% being under 20μm in length ( fig. S7). This length-to-width ratio separates ginger from most other Zingiberaceae.
(3) Fingerroot (Boesenbergia rotunda) Thirty-one starch grains from fingerroot (Type Ic) exhibit a triangular-ovate shape with a protruding hilum (Fig. 7, D-d; Fig. 8, D-d). Their lengths range from 19.1μm to 40.98μm. Although the shapes of some fingerroot starch grains overlap with those of ginger, 80% of the long axis diameters are larger than 20μm. Thus, the starch grains from these two species mostly can be distinguished ( fig. S7).
(5) Galangal (Alpinia galanga) Galangal starch grains (Type Ie) are narrow and oval with an eccentric center, and the cross arm is curved under polarizing light (Fig. 7, F-f; Fig. 8, F-f). This starch type is distinct in the ginger family.
(6) Clove (Syzygium aromaticum) Starch grains from cloves (Type II) are ovate with an eccentric hilum and visible lamellae (Fig. 7, G-g; Fig. 8, G-g). More than 300 pollen grains that share typical features with the Myrtle family have also been extracted from two newly excavated grinding slabs from Oc Eo (Fig. 7, I-K; Fig. 8, I-J). These are consistent with Syzygium in size, metrics and surface features (85,86,87). These pollen grains originated from clove buds.  Thirty-seven Type IV starch grains are characterized by their round shape, with a mean size of 11.31± 3.09μm, open hilum, radiating or linear fissures, and extinction crosses with slightly bent arms (Fig. 7, O-o). They resemble nutmeg starch (Myristica fragrans) (Fig.  8, N-n), and this shape is not associated with other spices.

Other plants (1) Rice (Oryza sativa)
More than sixty small Type V starch grains with polygonal shapes, centric hila, and straight cross arms share typical features with rice ( Fig. 7, Q-q; Fig. 8, O). In addition, phytoliths from rice leaves, stems, and husks were recovered in this study (Fig. 7, R-T), indicating local production and consumption of rice. These observations correspond with historical accounts that Funan people relied on rice agriculture for their fundamental subsistence.
(2) Palms (Arecaceae) Although spheroid echinate phytoliths from palms were found in the ancient samples analyzed (Fig. 7, U), actual starch grains from palms are absent. This suggests that palms were not targeted food plants in Oc Eo. Of special note, however, substantial quantities of spheroid psilate were discovered on a mortar (BTAG-2019) that also carried starch grains of gingers and other spices. These are spherical or ovate, of varied size, and present erosion holes on their surfaces (Fig. 7, V-W). Spheroid psilate arises as a vesicular infilling of epidermal and parenchyma cells in the foliage and reproductive organs of a wide range of Arecaceae, Poaceae, Cyperaceae, and gymnosperm species (77). In our modern reference collection, it could be observed in the seeds of species with high oil contents, such as mustard, cumin and coconut. The spheroid particles from coconut (Cocos nucifera) are especially comparable with our findings (Fig. 8, P).

Provenances and Permissions
The 40 analyzed stone implements were collected by the An Giang Provincial Museum before 2018 (n=20), and excavated between 2017 and 2019 by field teams from The Center for Archaeology, Southern Institute for Social Sciences, Ho Chi Minh City, led by Khanh Trung Kien Nguyen (n=20) (14). The sites excavated were Go Giong Cat, Lung Lon, and Go Sau Thuan, all located within the Oc Eo archaeological complex. Radiocarbon dates related these artifacts have been published by Khanh Trung Kien Nguyen and colleagues (24). In 2018 and 2019, the four authors selected the 40 specimens used in this study from the collections stored in the An Giang Provincial Museum and the Oc Eo Archaeological Field Station, southern Vietnam. Access to these materials was granted by the Center for Archaeology, Southern Institute for Social Sciences.    Two blue glazed ceramic sherds from West Asia; (K) A lug from a Chinese light green glazed "chicken head" wine jar found at Nen Chua, with a complete example (at right, but not from Oc Eo) stored in the Bac Ninh Museum (14).  Table S1, calibrated with OxCal v4.4.2 (88) and presented at 2σ probability.